When reading information from a DVD disc, the optical head of the DVD drive has to move accordingly in order to read the data on the different tracks of the DVD disc. Hence, the optical head of the DVD drive has to seek the tracks so that the laser beam emitted from the optical head of the DVD drive can move along different tracks and read the data successfully. In a typical disc, such as CD, DVD-ROM, and etc., data are only written on the grooves, while data can be written on both the grooves and the lands of a DVD-RAM disc.
Since data can be written both on the grooves and the lands of a DVD-RAM disc, the frequency of the mirroring signal (MIRR) projecting the tracks is twice the frequency of the MIRR of a CD or a DVD-ROM drive. Therefore, while a DVD-RAM drive is seeking the tracks, the frequency of the MIRR is twice the frequency of the track-error-zero-cross (TEZC) signal. Therefore, unlike the CD drive or the DVD-RAM drive, the DVD-RAM drive cannot utilize both the MIRR and the TEZC signals simultaneously to determine the direction of track-seeking and to provide the hysteresis protection while slipping.
Please refer to FIG. 1, which is a schematic diagram depicting the seeking architecture of a conventional DVD-RAM drive. In this seeking architecture 100, the seek controller 110 and the track controller 120 are used to receive a plurality of signals so as to direct the driver 130 to control the motion of the optical head 140. The plural signals include the speed error signal 151, the TEZC signal 153, the MIRR signal 157, and the track-error (TE) signal 159. The seek controller 110 controls the seeking of the optical head 140 according to the speed error signal 151, the TEZC signal 153, and the MIRR 157, while the track controller 120 controls the tracking of the optical head 140 according to the TE signal 159.
However, although the seek controller 110 can control the seeking of the optical head 140 according to the speed error signal 151, the TEZC signal 153, and the MIRR 157, but because the frequency of the MIRR 157 is twice the frequency of the TEZC signal 153, the seek controller 110 can not utilize the MIRR signal 157 and the TEZC signal 153 simultaneously for determining the direction of track-seeking and providing the hysteresis protection while slipping.
Accordingly, a method and apparatus for slip protection of DVD-RAM drive's seek control that is capable of controlling the motion of slipping and thus effectively stopping the slipping is surely desired.